We will continue a long-term research program in respiratory mechanics through four related projects: Micromechanics of the lung: The mechanical properties of lungs at the sub-acinar level will be studied by computer simulation of alveolar and alveolar duct geometry, tissue and surface forces. Airway aerodynamics: Further experiments testing wave speed theory of the limitation of maximum flow will be carried out in rubber tube models, excised airways, and intact lungs. Chest wall mechanics and respiratory control: Chest wall magnetometry will be used to study the implications of spinal flexion to volume change. Animal studies will be continued in which the nervous pathways involved in responses to altered mechanical advantage of respiratory muscles will be described. Development and evaluation of tests of pulmonary function: The slope ratio technique will be used to evaluate the implications of maximum expiratory flow-volume configuration in patients with acute and chronic airway obstruction. Also, the time dependence of maximum expiratory flow will be evaluated as an indicator of lung non-homogeneity.